Pressure-regulating device



June 1s, 194s. D. M. LAWRENCE 2,402,500-

l PRESSIURE REGULATING DEVICE Filed June 28, 1944 2 sheets-sheety 1 l I N VEN TOR. Dol'zdldM Lawrence B Y u 'ngi , WTsw June 18, 1946. D. M. LAWRENCE A 2,402,500

PRESSURE REGULATINGlDEVCE v Filed June 28, 1944 2 Sheets-Sheet 2 Y tpl n INVENTQR Y Dozza-IHM Laurreace wat. ATTORN EY Patented June 18,1946

PRESSURE-REGULATING nnvren Donald M. Lawrence, Newark, N.

Bendix Aviation Corporation, Teterboro, N.

J., assignor go a corporation of Delaware Application June 28, 1944, Serial No. 542,551

iciaim. l

My present application is a continuation inl part of my co-pendin'g application Serial No'.

' ina system wherein air at superatmospheric 422,601, Vled'December l1, 1941, and relates to l improved pressure regulating devices, and more particularly to an improved device for maintaining a predetermined pressure differential for the operation of air-driven instruments in a System for an aircraft, such as disclosed in my abovenoted co-pending application. v

Many instruments,` such as the directional gyro, gyro horizon, and turn indicator, are airdriven, and it is common to induce atmospheric air into tlie casing of each of these instruments directednat the conventional buckets carried. on

the rim of the gyro rotor and to exhaust the air at a definite suction pressure, so that the gyros may be spun with suilicient speed to carry out their diiferent indicating or control functions. Suction is usually applied to the exhaust of the casing by means of a vacuum pump, vwhich is usually driven directly from the engine. vi regulating valve to damp out fluctuations in the suction line pressure is normally applied to a suc- 2 tion manifold, to which each of the diierent airdriven instruments of the airplane is connected. The vacuum pump exhausts to the atmosphere.

It has been common to draw the air for driving the diii'erent gyroscope rotors from outside the aircraft and to maintain sufcient suction, that is, a minimum pressure diilerential between ,the external atmosphere and the pump input.

Due to the low air pressures obtaining at high altitudes, a positive displacement type of enginedriven pump, which is the type ordinarily used, is limited to the displacement of a lesser weight oi air per unit volume than it displaces at sea level. It will, therefore, be apparent that with increasing altitudes, the conventional system will have diiculty in maintainingthe required pressure diierential for driving the gyroscopic rov tors at constant speed;

It is an object of the present invention to -propressure is drawn throughthe casing of gyro instruments by a suction pump through a suction line, the regulating device having a novel means for relieving the load on the suction pump at' high altitudes, and also providing means whereby the suction line from -an instrument casing in a supercharged cabin may be exhausted to the atmosphere under certain regulated conditions for decreasing the load on the suction Dump.

Another object of my invention to provide a novel tubular means projecting longitudinally 'into the pump suction line from the differential pressure responsive device for more accurately reflecting changing ow conditions in the pump suction line so as to effect a more eicient control of the regulating device.

Another object of myl novel means for anticipating changes to be eifective on the instrument suction'line through A pressure changes in the pump suction line.

Further objects will appear from a study of the following specification when made in con-v junction with the attached drawings, throughout which like numerals designate like parts.

vide a pressure dierential regulating device for a system such as shown in my above-noted copending application, wherein the minimum pressure diilerential may be obtained regardless of the altitude of the system.

It is'a further object of the invention to provide a minimum pressure differential regulating device for use in conjunction with supercharged aircraft cabins, wherein, at increasing altitudes, the load on the suction or vacuum pump may be relieved.

Other objects include sure diiierential regulator the provision of a pres'- device adapted for use In the drawings, y Figure 1 is a sectional view of my novel pres sure regulating device taken` along the lines I-i of Figure 2. Figure 2 is an end view of lating device of Figure 1. Y

Figure 3 is a schematic showing of -a system in which the present invention is shown in operative relation. Y. Y

Referring to thedrawing of Figure 3 letter A indicates a supercharged aircraft cabin containing a plurality ci air-driven instruments B which instruments may for example be a rate oi' turn gyro, a, directional gyro and an artificial horizon. Each. of these instruments mayhave an air intake port C, which is open to cabin pressure, and their exhausts may be connected to a suction regulating valve D, which may be of the type shown in the Gregg Patent No. 2,194,749. Valve D connectstoja suction or instrument line E connected to a. suction pump F. The suction line E contains intermediate its ends a novel regulating valve assembly. The in detail and claimedin my copendingy application Serial No. 422,601 filed December 11, 1941, while the novel regulating valve forms the subject matter of the presentvapplication.

The novel regulating valve includes as shown inFigure 1 ahousing orcasting indicated by the invention 'is to provide the pressure regusystem' is described v numeral'I having formed therein a chamber 2 into which opens an input passageway 3 and an output passageway 4. l'I'he passagewaya normally connects tothe suction line E leading to the instruments within the cabin, previously noted, while lthe passageway 4 is normally connected to the input of the suction pump. The

passageway 4 is in constant communication with the passageway 3. through the chamber 2.

'I'he upper head portion of casting I is closed by a recessed plate 5, having a flexible diaphragm S extending across the recessed portion thereof. The plate 5 and diaphragm 8 are held in position between a cap 1 which is afilxed to the head por- 33 closed in a substantial conical point. while,

openings 34 are formed in the side thereof and subject to the negative pressure in the passageway 4, or suction force created by the flow or duid medium through the passageway 4. As shown in Figure 1, the iinger 32 is positioned concentric to the passageway 4 and in spaced relation to the inner surface of the passageway 4. The nger 32 8 are plates I3 and I4 fastened to the diaphragm 6 by a nut I5 screw threadedly engaged on a bolt I6 which 4projects through the plates I3 and I4 from one end of a stem I1.

The stem I1 projects through the plate 5 in slidable relation therewith. There are provided extends in the direction of flow of the uid medium through the passageway 4.

The openings 34 in the tubular iinger 32 are positioned in the passageway 4 a suilicient distance from the chamber 2, as to be unaiected by any turbulence created in the chamberr 2 due to the opening of the port I9. The finger 32 therefore senses changes in the negative pressure in the line created by the suction force resulting from the ow of uid medium through the pas- Isageway 4.

into the pump suction connection, the same anj Moreover, since the same projects ticipates changes to be made in the suction line connected to the passageway 3 due to variations in suction pumpl operation. In the operation of thedevice, the passageway 3 is connected by a suitable conduit to the air driven instruments such as a rate of turn gyro, a directional gyro or an artical horizon indicator mounted in a supercharged aircraft cabin and having an' air intake port open to cabin pressure, as described suitable sealing members 5A alxed to the plate i -5 and about the stem I1 to prevent leakage between the chambers 2 and I0.

The stem I1 has formed integral therewith at the opposite side a cylindrical gate valve I8 which controls a valve opening or port I9 leading from the chamber 2 into a recessed portion of the casting I. Closing the recessed portion of the cast- `-ing I is a recessed casting 20 cooperating therewith to form a chamber 2|. 'I'he casting 281s afxed to ,the casting I by suitable bolts 22.

Formed in the casting 20 is a sleeve 23 in which is slidably mounted the cylindrical gate valve I8. A helical spring 24 acts at one'end upon the cylindrical gate valve I8 biasing the same in a direction for normally closing the valve opening I9.

'I'he helical spring 24 is supported at its opposite end by a, plate 25' which is locked against rotary movement by splines 26. 'Ihevplate 25 may be adjusted rectilinearly by rotation of a screw 21 which is screw threadedly engaged in the member 25. The screw 21 is conveniently connected to an adjustment member 23 mounted exteriorly of the casting 2|, whereby the tension of the spring 24 ,may be readily adjusted for calibration purposes.

'I'he chamber 2| has leading therefrom a passageway 29 formed in the casting 2l and normally connected to the atmosphere.

The stem I1 has formed therein a channel 30 leading from the interior oi.' the cylindrical gate valve I8 and opening through ports 3l into the chamber 2, whereby the pressure within the interior'of the cylindrical gate valve I8 is substantially equal to the pressure within the chamber 2.

There is further provided a curved tubulin4 member or finger 32 which opens at one end into the interior ofthe chamber I8 and is amxed in any suitable manner to the plate 5. The tubular ilnger 32 extends from the plate l and is curved so as to project longitudinally into the passageway 4.

The linger 32 has the longitudinal end thereof in my co-pending application filed December l1, 1941.

A suction pump is connected through a suitable suction line to the passageway 4, whereby Serial N0. 422,601.

lair at sub atmospheric pressure is drawn through the chamber 2, passageway 3, and air intake ports of the air-driven instruments mounted in Aunder certain regulated conditions.

the supercharged aircraft cabin.

However, in order to maintain a substantially minimum constant differential pressure between the pressure in the instrument suction line connected to the passageway 3 and the pressure in the supercharged aircraft cabin, a valve I8 is provided whereby the suction line from the instrument casing may be exhausted to the atmosphere The valve serves the further purpose of decreasing the load on the suction pump as the atmospheric pressures decrease upon rise in altitude. Thus upon maintaining a constant cabin pressure greater than surrounding atmospheric pressure 'at the high altitudes, the decrease in atmospheric pressure may be utilized through operation of the unloading valve I8 to maintain the suction line at a predetermined' minimum constant diil'erential below the supercharged cabin pressure in such a manner that the' load onthe pump and the corresponding power requirements may be decreased materially. Thus a pump which may serve as a source oi' suction at the lower altitudes may through the operation of my novel unloading valve be gradually relieved of work as the altitude f increases so that the powerrequired to drive the suction pump at high altitudes may decrease to practically zero.

In order to maintain the predetermined diiIerential between supercharged cabin and line pressure (suchas a pressure differential of six inches oi' mercury) the diaphragm 8 has cabin pressure applied through conduit I2 and port I I to the chamber 8, and a pressure indicative of line pressure applied at the chamber I8. The diaphragm I is arranged to operate the valve I8 in response to a predetermined differential between the pressures applied in chambers 8 and I0. T hus as the supercharged cabin pressure in the chamber 3 5 j i increases over the pressure in the chamber I the diaphragm 3 is biased by such cabin pressure -against the tension of the spring 24 so as to In order to obtain a measure of the valve of A the pressure in the suctionline free of the turbulence and linaccuracies introduced upon opening of the sleeve valve I8 the measurement of the pressure in the suction line is taken ata point other than in the chamber 2. Moreover, in order to anticipate changes which may be caused in such pressure through variations in the suction pump operation. I have found the point for most eiective measurement to be in the passageway I rather than in the passageway 3 and at a point an appreciable distance from the chamber 2.

In order to effect this measurement so as to produce an anticipating effect on the valve I8, I have provided the tubular nger 32 which opens at one end into the chamber 4.

The tubular nger 32 as explained extends from the plate 5 and is curved so as to project longitudinally into the passageway II extending in spaced relation to the inner surface 4A. Through the openings 3l, a negative or suction pressure is exerted through the tubular linger 32' on the chamber I0. 'Ihis pressure represents not the actual pressure in the instrument suction line 3 but rather an indication of what such pressure may be unless adjustment of the valve I8 is effected to correct for variations in atmospheric pressure or pump operation. Thus when such anticipated line pressure approaches a maximum predetermined pressure differential below supercharged cabin pressure, the diaphragm 6 is biased by the cabin pressure so as to open the valve I8 permitting an unloading of the pump to atmosphere through the passageway 29. The opening of the valve I8 causes the pressure within the suction line to increase so as to approach atmospheric pressure until the suction line pressure and cabin pressure once again are within the predetermined diierential pressure range.

From the foregoing it will be readily seen that by means of my novel tubular ngeror sensing 6 device 32, an anticipating effect is produced on the regulating device 6, hereby a corrective regulation of the unloading valve I9 is effected before an adverse change takes place in the instrument suction line, and thus providing a more accurate regulation of the suction line unloading valve.

While only one embodiment or" the present invention has been shown in the drawings, it is to be understood that various changes may be made without departing from the scope of tjhe present invention. For this reason, it is intended not to limit the invention by the description hereinlgiven as an example, but solely by the scope of the appended claim. l

What is claimed is: v

In a'suction relief valve, the combination of a body having a .chamber and a plurality of means adapted to operatively connect the chamber with suction and with a respective line in which the suction is to be regulated, the arrangement being such that the chamber acts as conduit means for continuously connecting each of said means together, said body also having port means disposed on one side of the chamber conduit means for relieving suction in the chamber by admitting flow of air from the atmosphere through said'port means, a valve constructed to cooperate with the relief port means to throttle the ow of air through said port means, said valve being of the pist'on-poppet type arranged to have one side subjected to the pressure in the chamber and pro-` vided with a connection through the piston to introduce an equalizing pressure to its other side, a spring on the same side of the chamber conduit means asthe valve and connected with the valve to bias the valve in the direction to decrease the effective opening of said port rmeans, a tube having one endv located away from/the wall of the suction connecting means and constructed to transmit the pressure within the last-mentioned means to the other end of said tube,and means on the other side of the chamber conduit means adapted to be sensitive to the diiference between vthe pressure within said tube and a higher reference pressure and connected to the valve to tend to increase the effective opening of said port means upon an increase of said dierence.

DONALD M. LAWRENCE. i 

